@uid is the target of the Free/Busy request.
@e is the end date.
@s is the start date.

And I believe username is the user to initiate the request from. Since you can hide free/busy info in some situations, not all users would be able to see the target's freebusy info.

In this example, the long date codes such as 1350499000000 and 1350050243000 are unix epoch times (1350499000 or Wed Oct 17 14:36:40 EDT 2012) with three additional digits on the end (000) representing milliseconds.